Many electronic systems for usage in various applications such as network communications, telecommunications, data transmission, and many others are susceptible to damage resulting from transient energy. Lightning and other transient energy events can create rapid electrical energy transients. Such transient events can damage electronic circuits or equipment. It is common in such instances to use isolating transformers and/or external transient suppressor devices to ensure the sensitive physical (PHY) layer devices are not damaged. In certain cases it may be desirable to remove the transformer and surge suppressor and replace them with non-isolated devices.
Once the isolator is removed it is necessary to provide an alternative means of suppressing surge. This can be accomplished by surge isolating the supply to the sensitive PHY circuit via a power transformer. Some circuit arrangements include two or more circuits that are connected but operate with reference to ground levels that may be different. In response to various conditions, electrical current may flow between different ground domains so that the ground levels can move with respect to one another, which may be a source of common-mode noise. In a communication application, the generated noise creates undesirable emissions that violate regulatory standards.